I might like to use an Arduino as a remote control to a raspberry pi. I want a device with a d-pad a number pad and maybe a handful of other buttons. A small low powered temporarily on display only needing to display while used. I want a wireless tech that can pass through walls. I'd like to use my pi like a tv box. I love my logitech harmony 665 remote layout and ease of use and would like to emulate some of it's better features to a pi. I particularly like the idea of it's display although I don't need multi color. Single color low powered would be great. Maybe LCD or is there another tech that is less expensive and lower power draw? They have four buttons around the display and show on the display which each of those 4 buttons does. I would like to emulate that aspect and a bit more. I would like to use batteries like a remote as well. Although maybe rechargeable. I would like to go at least a couple weeks without having to recharge and ideally 3 months or more. I am familiar with programming an arduino.
I can program all this easy. what I am looking for is:
A.) is the arduino a good fit for what I am trying to do?
There is always going to be something better maybe a pico (are these more or less power hungry than a arduino)?
B.) Powering such device? am a being too optimistic on my use case like a remote?
C.) good low powered transmitter? I should really only need to transmit after programming I'd like to plug in to change programming as I add new functionality.
D.) Ideas on how to make the physical device to fit in my hand like a remote does.
Can I get a number pad and d-pad board pre-made that has a comfortable feel like a remote? What about the rubbery like buttons on a remote?
Starting to think this project might get more expensive than a cheap cell phone 
I have a web interface already that works on a simple browser. I was looking for an inexpensive remote.